PATENT LITERATURE 1 describes a technique of “assigning an upper bit-plane group as a base layer, and a bit-plane group having the larger number of bits including the upper bit-plane group as an enhancement layer in a plurality of bit-planes that give image data when hierarchically encoding a moving image, and generating encoded data of the enhancement layer by encoding a difference between the layers of a differential picture by prediction in the enhancement layer and a differential picture by prediction in the base layer in the enhancement layer” (see [0007] in PATENT LITERATURE 1) as a solving means for an object of “providing an encoding technique to efficiently performing encoding by imparting a pixel depth different for each moving image” ([0006] in PATENT LITERATURE 1).